Operators for program control

Abstract

Structured programming constructs such as if-then-else and do-while have traditionally been used to give a natural flow to programs written in one of the ALGOL-like languages. Languages with a functional basis, such as APL and LISP, provide (and are characterized by) alternative means of controlling the flow of expression. These include function modularity, the application of functions across data structures, the use of data structures to control program flow, and the mapping of operations across data and across other operations. In APL2, the use of these methods has been enhanced by the generalization of APL data structures, the addition of the primitive operator Each(″), and the ability to define operators. This paper will examine ways in which these features may be used to give a non-procedural look to APL2 functions.